1. Field:
The present invention relates to electrosurgical apparatus of the type typically used in surgical operations for coagulating biological tissue, and provides a device for use with such electrosurgical apparatus.
2. State of the Art:
Electrosurgery is a known technique for performing cutting and coagulation procedures during surgical operations. Radio frequency (rf) current supplied by an electrosurgical generator is conveyed to a patient through the use of specialized electrodes. For example, a pair of such electrodes may be formed as opposing prongs or legs of a bipolar forceps. Reliable control of the temperature of each prong is essential. Otherwise, when the prongs are used for coagulation, tissue adhesions may result; particularly if one of the prongs is inserted further into the biological tissue than is the other prong. In such instances, the prong that is inserted to a lesser extent tends to become hotter, thereby increasing the risk of adhesions at its contact tip. If the temperature at a prong rises to above 80.degree. C., the forceps may actually become destructive of a surgical procedure which the coagulation procedure is intended to support.
To minimize the likelihood of overheating, it has been suggested to place temperature sensors near the contacting face of the coagulating instrument. For example, U.S. Pat. No. 4,685,459 suggests embedding thermocouples as thermosensors in the machined tips of a coagulating forceps. This type of construction is relatively expensive to manufacture. Because the thermocouple is separated by insulation from the forceps, the response time of the device is reduced. Moreover, the device is inherently susceptible to the problems associated with breakdown of the electrical insulation between the thermocouple and forceps.
U.S. Pat. No. 3,685,518 discloses a surgical forceps designed to prevent the terminal parts of the forcep jaws from overheating. The disclosure of U.S. Pat. No. 3,685,518 is incorporated by reference in this disclosure for its description of bipolar high frequency surgical devices, the hazard of overheating associated with the use of such devices, and the importance of materials selection and configuration of parts in the design of such instruments.
U.S. Pat. No. 4,041,952 discloses an electrosurgical forceps with mechanical switching means carried by the tines (legs) of a forceps. Electrosurgical energy is applied to the contact surfaces (tips) of the tines by finger pressure applied to the tines to close the associated switching means.
U.S. Pat. 4,662,369 discloses a safety circuit for an electrosurgical apparatus. The circuit functions to sense rf current leakage and to respond by redirecting the output of the rf source (generator), thereby to limit leakage to below a predetermined value. The disclosure of U.S. Pat. 4,662,369 is incorporated by reference in this disclosure for its general description of electrosurgical techniques and the hazard inherent to such techniques of electrical burns.
U.S. Pats. 4,671,274; the aforesaid 4,685,459 and 4,686,908 are each directed to bipolar electrosurgical instruments of specialized design. These patents, the disclosures of which are incorporated by reference as a part of this disclosure, describe the components and uses of instruments of this type.
A number of instruments currently supplied by F. L. Fischer, Fischer MET GmbH, Schopfheimer Str, D0-7800 Freiburg, Federal Republic of Germany, are disclosed in a brochure entitled "New Dimensions in Bipolar Coagulation." The brochure describes an rf generator and associated hand pieces which purportedly eliminate burns and tissue sticking to the instrument tips. Thermosensors are integrated in the tips of the coagulation instrument to continuously measure the contact temperatures between tissue and metal. Microprocessors continuously respond to ensure that the temperature remains constant throughout the coagulation procedure.
In spite of the advances in electrosurgical techniques reported by the aforedescribed patents and commercial instruments, there remains a need in the electrosurgical art for an improved temperature sensing forceps. In particular, there remains a need for such an instrument which avoids the problems associated with electrically insulating thermocouple elements from rf-carrying prongs (legs, tines) of the forceps. The temperature-controlled (sensing) forceps available currently remain expensive and difficult to manufacture, are characterized by delayed response of the thermocouple elements by virtue of the insulating material, and are susceptible to electrical breakdown (of the insulation) between the thermocouple elements and the prongs.